The National Household Survey on Drug Abuse (NHSDA) represents a major effort to monitor drug use in the population. Results from the surveys are released annually, providing important information about the prevalence of use in the general population and changes in prevalence over time, but no information on problematic use, reflected in dependence and abuse. Although data on dependence symptoms and functional impairment are collected in the surveys, these data remain to be analyzed. This proposal requests four years of support to carry out secondary analyses of multiple waves of the NHSDA to capitalize on the data available in the surveys to investigate several issues related to substance dependence and abuse. Algorithms will be developed to generate approximations to DSM-III-R and DSM-IV definitions of substance dependence and abuse by the American Psychiatric Association. Six questions will be investigated. (1) The-extent of drug dependence and abuse in the U.S. population and across different groups, in particular age, sex, and racial/ethnic groups. (2) The relationships of dependence and abuse to extent of use as reflected in quantity/frequency measures of drug use for four drug classes: marijuana, cocaine, cigarettes and alcohol. (3) The relationship between dependence and abuse and progression along the developmental sequence of involvement in drugs. (4) The relationship between dependence and abuse and participation in treatment programs. (5) The extent of familial similarity on drug use and dependence be.tween parents and adolescents, and siblings. (6) The relationship between the overall prevalence of drug use in the nation and rates of dependence and abuse. All analyses will be conducted for the total population, and for age, sex and ethnic-specific groups. It is hoped that the analyses will elucidate why minorities, especially African-Americans, are overrepresented in morbidity and treatment cases and the age and cohort-related differentials in prevalence of use reported by African-Americans compared with whites. The analyses will be based on several waves of data: N 1991 = 32,594, 1992 = 28,832, 1993 28,000 (and in more limited way the 1985 wave N = 8,038). By aggregating data from 3 surveys, we expect 5,100 parent-child and 2,700 sibling pairs. The oversampling of youths and minorities and the large number of minorities included in the NHSDA make possible age- and racial/ethnic- specific analyses that are rarely feasible in any other study. The clustering of interviews within households with a youth 12-17 years old provides dyadic samples of related household members. The repeated nature of the assessments allows for historical trends to be taken into account in the assessment of drug dependence/abuse prevalence. The study will extend our understanding of the extent of serious drug use in the nation, the etiology of substance dependence/abuse, the extent of treatment needs, and racial/ethnic differences in patterns of use, dependence/abuse, morbidity and treatment experiences. Despite their importance, such questions by and large have not been treated in the epidemiological literature on drug use in the general population, which has focused almost exclusively on frequency measures of drug use.